How to make relational database has the semantic character, and how to describe the semantic of object, are important problem during the application of semantic web. In this paper, a model of Ontology-Object-Relational mapping rules and algorithms was also presented. Based on ORM, the mapping and transformation between ontology, object and relational database was realized. A system for experiments had been developed, and the experiment for the transformation between relational database and ontology instances was conduct, the result show that the mapping model, the mapping rules and the algorithms are right and feasible.